Not natively, no. At this time, TIdHTTPServer only implements BASIC authentication directly.

You can use the TIdHTTPServer.OnParseAuthentication event to implement custom authentications. For instance, by using Microsoft's SSPI API to handle NTLM/Kerberos authentication. Though, NTLM requires multiple HTTP messages back and forth, which you would have to handle manually, as TIdHTTPServer does not really handle when a request requires multiple messages to complete authentication.